Common Misconceptions of human evolution
- Our ancestors were chimpanzees:
WRONG!
-
RIGHT: We share a common ancestor with chimps
- Human evolution = series of steps from ancestor to Homo sapiens:
WRONG!
-
RIGHT: Hominid phylogeny is more like bush than a ladder
- Homo sapiens is a twig on the bush
- Human characteristics like upright posture and large brain evolved together:
WRONG!
-
RIGHT: Our ancestors include upright walkers with small brains



The big picture: Humans are evolutionary newcomers
- Our closest living relatives are the chimpanzees
- common ancestor with chimps ~ 6-7mya
- genomes are 98-99% similar to chimps
- 1% difference means a lot!!
- 19 regulatory genes differ
- Hominin derived characters:
- bipedal
- large brain…
- reduce jawbone and jaw muscles
- shorter digestive tract
- These characters are not unique to Homo sapiens!

Hominins: part of primate family; includes genus Homo
- ~20 species of fossils
- brain size, teeth shape, body size
- inferred tool use/culture/language
- species had different combos of each
- Really old fossils
- Sahelantrophus tchadensis (Toumai): 6.5mya
- fossil connection to Homo missing
- Ardipithecus ramidus (Ardi): 4.4 mya
- lived in trees & on ground
- We (Homo sapiens) are the sole surviving lineage

Hominin evolution was not a linear process

Hominin evolution: brain volume

Hominin evolution: The jaw


Brainstorm: Why did we evolve to walk on 2 legs?



The earliest Hominins evolved in Africa
- All but the 4 most recent species are found on the African continent
- Oldest hominin fossil found in Chad
- ~6-7 mya, found in 2001
- diverged from common ancestor with chimps (~7mya)
- Hominin diversity increased ~4-2 mya
- Australopithecus spp
- ‘Lucy’ fossil in Ethiopia
- definitely bipedal
- gorilla-like shoulders: climbers
- possible tool use

Lucy (Australopithecus afirensis) direct ancestor of Homo?

Homo genus in the fossil record
- Early Homo genus is composed of first humans
- all species are called humans
- ~2mya to present day
- 8-10 species described!
- flat and narrow faces
- small jaws and teeth
- larger brain cases
- Tool-making was their hallmark

Brain volume in Homo species increased disproportionately

Species of Hominins and Homo overlapped!

Homo species left Africa (H.ergaster then H.erectus)

Homo sapiens evolution
- Descended from a 2nd wave of immigration out of Africa
- ‘Out of Africa’ hypothesis
- ~100,000 ya
- fossil and DNA evidence
- not the first species to leave
- 1 population left Africa, split into 3 groups
- Natural selection for the ability to reason and communicate
- Increased tool use and language
- resulted in larger brains

H.neandertalensis and H.sapiens co-occured
- Neanderthals evolved in Eurasia
- Split from a common ancestor ~ 500,000 ya
- buried dead
- used art
- Co-existed until ~ 30,000 years ago
- Only one lineage survived
- Interbreeding
- Competition?
- Extirpation of Neanderthals by modern humans?

H.neandertalensis and H.sapiens co-occured


Recent findings: new modern species?
- Really small new species (H.floresiensis)?
- fossils in Indonesian island cave
- allegedly 13,000 years old
- Archaeologists seeking path to Australia
- Controversy: diseased H.sapiens?

Where is Human evolution heading?
